By Lord Acchvry. 487 



subgiobiilar or spherical, smooth, 

 subglobular or spherical, smooth. 



at first spherical, afterwards 

 various, smooth. 



spherical, smooth. 



When it is remembered that the spherical form though common 

 is not very common, the evidence of this table is overwhelming. 



There are no doubt a few cases for which as yet no explanation 

 is forthcoming. Such for instance as the Oak, the Plane, and 

 among Composites, Artemisia, Gnaphalium, and some others. 



The allied genera Salir (tlie Willow) and Populus (the Poplar) 

 afford an interesting illustration. In Scdix the pollen is carried 

 by insects, and is of the common elliptic three-lobed form, while 

 in Po-puliLS the pollen is wind-borne and spherical. 



I do not know of any true windflower with spiny pollen, though 

 XantTiium trifidum is a near approach to it. 



The cases in which some species are entomophilous and others 

 nearly allied are anemophilous present specially interesting ex- 

 amples. 



For instance, the Eosaceee for the most part have elliptic 

 pollen. Potcrimn sa7ignisorlxi, however, is a wind-fertilized flower, 

 and the pollen is spherical. 



Among Composites, also, Artemisia, Gnaphalium, and some 

 allied genera present interesting transitions. Gnaphalium leonto- 

 podium, the Edelweiss, has spherical and apparently, according to 

 H. Miiller's figure, smooth pollen. On the other hand, G. idiginosum 

 has elliptic pollen, as have Hclichrysum arenarinm, and Artemisia 

 vulgaris. Warnstorf says of Artemisia absinthium, A. vulgaris, 

 and A. cavipestris, " Polleuzellen rund bis elliptisch." 



Spherical pollen of entomophilous species is not, however, in all 

 cases spiny. Some Taxonias are spherical with a coarsely netted 

 surface. The pollen of some Opuntias is spherical and densely 

 granulated ; that of Mesemhrnanthemum is spiny in some species, 

 granulate or even smooth in others. 



In wind-fertilized flowers the stigmas as a rule are feathery, and 

 it is interesting that this is the case with some species of Artemisia. 

 alone, or almost alone, among Composites. 



Spherical and Spiny Pollen. 



Spherical and spiny pollen occurs in a large number of species 

 which are adapted for fertilization by insects, as for instance in 

 many, or most, Compositse (figs. 15, 16, 55) and Malvaceae, many 



